Her three claims were: that opposition to same-sex marriage is essentially homophobia; that the Australian people cannot be trusted to have a respectful discussion about such matters; and so the matter should be left to the parliament.

Is it true that all defenders of the traditional definition of marriage act out of “condemnation … animosity … casual and deliberate prejudice… [and] hate” towards same-sex attracted people, as Penny Wong suggests? Well, until a few years ago the senator herself opposed the redefinition of marriage; so did her leader Bill Shorten; and so did a number of other political leaders. I do not think they were being hateful bigots at that time.

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Presumably, their views of marriage and family, or of the needs of same-sex people, or of the proper role of the state and culture etc then supported leaving marriage as it was; presumably, over time they were persuaded differently. Others still hold the position these leaders previously held: why presume they are driven by hate? Could it not be that they have real reasons for supporting the traditional conception of marriage? And real questions about the proposed alternative?

Only a decade ago same-sex marriage was a radical proposal with little support among the major parties or general population. The then Penny Wong was in the vast majority. Shifting opinion might be explained by growing sympathy for those with same-sex attraction or changing views (and increasing confusion) about the meaning of marriage. But another reason might be that people have felt pressured into supporting this social change (or cowed into silence) by fear they will be tagged “bigot” if they don’t.

The fact is that many ordinary Australians are both pro-gay people and pro-traditional marriage. They know and love people with same-sex attraction and want only the best for them. They know that such people have often suffered injustices in the past and sympathise with the complaint that something is being denied to them still. But they also believe that marriage is a unique relationship that unites people of the opposite sex as husband and wife and, more often than not, as father and mother. Such ordinary Australians are not bigots.

Senator Wong’s second claim is that Australians can’t be trusted to have a respectful discussion or to come to a reasonable decision about such matters, insisting that a plebiscite “will instead license hate speech”. So, too, opposition leader Bill Shorten. Yet as recently as in 2013, Mr Shorten said he was “completely relaxed” about holding a plebiscite, preferring to let the people of Australia make the decision rather than 150 MPs. Yet this week he has characterised the plebiscite as “taxpayer-funded … green light to homophobia and ugly hateful attitudes.”

Once levelled and much repeated, this charge gathers momentum and becomes the new orthodoxy: all dissent is dismissed as “religious”, “groundless” and “hateful”. Combined with the claim that “history” or “the public” or the most enlightened nations have already spoken definitively in favour of same-sex marriage, this disempowers and intimidates ordinary people who might otherwise articulate a different view.

Some seem more optimistic about the charity and common sense of Australians. The Chair of Australian Marriage Equality, Alex Greenwich MP, has expressed his hope that whether it’s a plebiscite or a parliamentary vote Australians will “have a peaceful and respectful national conversation”. Likewise President Obama, though now a same-sex marriage advocate too, argues that those who understand marriage to be a male-female union are “not mean-spirited’”. Indeed, “a bunch of them are friends of mine,” he added, “you know, people I deeply respect.” They just have “a different understanding” of what marriage is “because they care about families.”

What is that different understanding? It is one that says that among all committed relationships the union of two persons of opposite sex has the unique capacity to bring new life into the world and to give those children the benefit of being raised by their own mother and father.

Of course, not all marriages see children – though all married couples do the sorts of things that lead to children. Of course, no family situation is perfect. And, of course, there are other relationships worth honouring. Nonetheless, as every culture in history until now has recognised, it is worth uniting men and women in marriage not just for their sake but for the sake of any children resulting from their marital acts. To weaken understandings of and support for marriage even further, will be to deny people the opportunity and ability to live that particular relationship.

Senator Wong’s third claim is that the Australian parliament would be better than the Australian people at debating such matters rationally and without rancour. My own view is that we could all benefit from the kind of national conversation a plebiscite should occasion. Public discourse is enriched, not degraded, when people learn the reasons why others hold contrary views on any given matter and learn how to express those differing reasons within the context of civic friendship and reasonable disagreement.

In any case, we hold referenda before making major changes to our legal constitution; a plebiscite seems not inappropriate before making an unprecedented change to our social constitution. The family based on the marriage of man and woman has been the fundamental cell of Australian society since its inception. Those who propose to change this radically are asked by the plebiscite to give reasons sufficient to persuade not just politicians but the whole Australian community. I am confident we can conduct such a conversation charitably and wisely.